Plants are constantly exposed to a variety of biotic (e.g., pathogen infection and insect herbivory) and abiotic (e.g., high or low temperature, drought, flood, anaerobic conditions and salinity) stresses. To survive these challenges, plants have developed elaborate mechanisms to perceive external signals and to manifest adaptive responses with proper physiological and morphological changes (Bohnert et al., 1995). Plants exposed to heat and/or low water or drought conditions typically have low yields of plant material, seeds, fruit and other edible products. Some countries of the world consistently have very low rainfall and therefore have problems growing sufficient food crops for their population. Yet it has been observed that some plants survive and thrive in low water environments. It would, therefore, be of great interest and importance to be able to identify genes that confer improved water efficiency characteristics to thereby enable one to create transformed plants (such as crop plants) with modulated water efficiency characteristics to, thereby, better survive high and/or low heat, high and/or low water, and drought or flood conditions. Exogenous application to plants of high concentrations of PEG and mannitol are known to produce osmotic stress resulting in the retardation of growth and vigor and are used to assess drought responses. Exogenous application of ABA stimulates drought-responses in plants and can, therefore, be an important screen to identify genes that confer improved water efficiency.
In the field of agriculture and forestry efforts are constantly being made to produce plants with an increased growth potential in order to feed the ever-increasing world population and to guarantee the supply of reproducible raw materials. This is done conventionally through plant breeding. The breeding process is, however, both time-consuming and labor-intensive. Furthermore, appropriate breeding programs must be performed for each relevant plant species.
Progress has been made in part by the genetic manipulation of plants; that is by introducing and expressing recombinant nucleic acid molecules in plants. Such approaches have the advantage of not usually being limited to one plant species, but instead being transferable among plant species. (Zhang et al. (2004) Plant Physiol. 135:615). There is a need for generally applicable processes that improve forest or agricultural plant growth potential. Therefore, the present invention relates to a process for increasing the abiotic stress tolerance and consequently the growth potential in plants, characterized by expression of recombinant DNA molecules stably integrated into the plant genome.